1. Field of the Invention
The invention relates to vehicle suspensions and, more particularly, to mounting brackets for mounting a trailing arm in a trailing arm suspension system to a vehicle frame.
2. State of the Prior Art
A typical suspension system for a heavy duty vehicle, such as a semitrailer, comprises a mounting bracket mounted to the underside of the vehicle frame, a trailing arm pivotably mounted to the bracket and extending rearwardly, an air spring mounted between the rear end of the trailing arm and the frame, and an axle mounted to the trailing arm intermediate the air spring and the bracket.
A typical prior art mounting bracket and its attachment to a vehicle frame are shown in FIGS. 1 through 3. The bracket 10 comprises a U-shaped side frame 12, a U-shaped top plate insert 14, and front and rear gussets 16 and 18. When the bracket 10 is mounted to a vehicle frame, it depends therefrom such that the side walls 13a, 13b of the side frame 12 are oriented vertically and its open end 15 faces rearwardly. A portion of the rear edges 20 of the side frame 12 slopes forwardly and has outwardly extending flanges 21 to provide added stiffness to the sidewalls 13a, 13b of the side frame 12. The top plate insert 14 fits within the side frame 12 to further stiffen the bracket 10. The top plate insert 14 comprises a top panel 22 which fits tightly within the U-shaped frame 12 at its upper edges, a vertical panel 24 extending downwardly from the top panel 22, thereby enclosing a portion of the open rear of the side frame 12, and an angled panel 26, sloping forwardly within the side :frame 12. The edges of the top plate insert 14 are typically welded to the surfaces of the side frame 12. The front and rear gussets 16 and 18 extend outwardly from the U-shaped frame 12 at its front and rear, respectively, and angle upwardly to be rigidly secured to the vehicle frame and thereby brace the bracket 10. Holes 28 in both sides of the side frame 12 near its lower edge are adapted to receive a pin for rotatably mounting the trailing arm. The upper edges of the side frame 12 and the front and rear gussets 16 and 18 are further secured to the vehicle frame by welding.
Turning now more particularly to FIG. 2, the top panel 22 of the top plate insert 15 is frequently elevated above the upper edges of the side frame 12. A fillet weld 30 permanently affixes an edge of the top panel 22 to a corresponding edge of the side frame 12. The weld 30 is often uneven and must be ground after assembly to render it smooth and flush with the top panel 22. Typically, the bracket 10 is separately assembled in a fixture and attachment of the bracket 10 to a vehicle frame 32 comprises a second operation wherein an additional fill-in weld 34 secures the first weld 30 and the top panel 22 to the vehicle frame 32. In some cases, where the top panel 22 is flush with the top edges of the side frame 12 or, as in FIG. 3, the top panel is altogether missing, the upper edge of the side frame 12 abuts the vehicle frame 32 directly and fillet weld 36 secures them together. Fabrication of trailing arm suspension systems as in FIG. 2 requires at least two assembly operations, four parts, and intense labor just to manufacture a mounting bracket. There is a continuing need for lower manufacturing costs, higher strength, and lower weight in vehicle trailing arm suspensions.